Cocatalyst versus Precatalyst impact on the Vinyl-Addition Polymerization of Norbornenes with Polar Groups: Looking at the other Side of the Coin

2021 ◽  
Author(s):  
Evgeniya Bermesheva ◽  
Ivan Nazarov ◽  
Ksenia Kataranova ◽  
Anna Khrychikova ◽  
Danil Zarezin ◽  
...  
Keyword(s):  
The Other ◽  
Membrane Processes ◽  
Polar Groups ◽  
Addition Polymerization

Polymers derived from norbornenes with polar groups are of interest as modular templates and materials for membrane processes and microelectronic applications due to the attractive combination of their properties. However,...

scholarly journals Comparative studies of the specificities of α-chymotrypsin and subtilisin BPN′. Studies with flexible and ‘locked’ substrates

1972 ◽  
Vol 126 (3) ◽  
pp. 659-665 ◽  
Author(s):  
T. N. Pattabiraman ◽  
W. B. Lawson
Keyword(s):  
Methyl Ester ◽  
Carbon Atom ◽  
Binding Site ◽  
Comparative Studies ◽  
Detrimental Effect ◽  
Optically Active ◽  
The Other ◽  
Optical Isomers ◽  
Polar Groups ◽  
Hydrolysis Of

Subtilisin BPN′ hydrolysed N-acetyl-l-3-(2-naphthyl)-alanine methyl ester, N-acetyl-l-leucine methyl ester and N-acetyl-l-valine methyl ester, faster than α-chymotrypsin. Of eight ‘locked’ substrates tested, only methyl 5,6-benzindan-2-carboxylate was hydrolysed faster by subtilisin, whereas the other esters were better substrates for chymotrypsin. Compared with the values for chymotrypsin, the stereospecific ratios during the hydrolysis of the optically active locked substrates by subtilisin were decreased by one and two orders of magnitude for bi- and tri-cyclic substrates respectively. The polar groups adjacent to the α-carbon atom of locked substrates did not contribute significantly to the reactivity of the more active optical isomers, but had a detrimental effect on the less active antipodes during hydrolysis by both the enzymes. These studies show that the binding site of subtilisin BPN′ is longer and broader than that of α-chymotrypsin.

scholarly journals Development of partial miscibility in polycarbonate/polypropylene blends via annealing

2017 ◽  
Vol 37 (7) ◽  
pp. 707-714 ◽  
Author(s):  
Sani A. Samsudin ◽  
Catherine A. Kelly ◽  
Stephen N. Kukureka ◽  
Mike J. Jenkins
Keyword(s):  
Mechanical Properties ◽  
Infrared Spectroscopy ◽  
Infrared Spectra ◽  
Dynamic Mechanical Properties ◽  
The Other ◽  
Partial Miscibility ◽  
Polar Groups ◽  
Polypropylene Blends ◽  
Pp Blends ◽  
Polymer Interaction

Abstract The morphology, dynamic mechanical properties and infrared spectra of polycarbonate (PC)/polypropylene (PP) blends were investigated. As expected, PC and PP were immiscible when blended together; however partial miscibility developed following annealing. The miscibility of one polymer in the other was examined using the modified Fox equation and the values of the Flory-Huggins polymer-polymer interaction parameter (χ12) were also calculated following the Kim and Burns approach. Moreover, the possible causes for partial miscibility in the annealed PC/PP blends were explored by infrared spectroscopy. It was concluded that annealing caused degradation of PP, leading to the formation of polar groups which were then able to interact with PC generating regions of partial miscibility.

The ultrastructure of a dental composite resin

1988 ◽  
Vol 46 ◽  
pp. 940-941
Author(s):  
J.E. Laffoon ◽  
M.E. Jensen
Keyword(s):  
Composite Resin ◽  
Ultrastructural Level ◽  
Dental Composite ◽  
The Other ◽  
Tooth Structure ◽  
Addition Polymerization ◽  
Dental Procedures ◽  
Dental Composite Resin ◽  
The Many ◽  
Missing Tooth

Methacrylate has been used as a resin with exceptional cutting quality for electron microscopy, but suffers from problems of stability in the electron beam. On the other hand, one of the areas it is used is as a synthetic resin where it is increasingly becoming a factor in the restoration of missing tooth structure in dentistry. All the resins used in dental procedures are produced by “addition polymerization”, that is once the polymer is produced it consists of a sequence of identical monomers. The resin is then “filled” with particulate matter to increase it's strength and stability, such as silica. Of the many available resin systems used presently in dentistry, three were chosen for this study. One is a Type II composite, and the other two are classified as microfilled. The aim of this study is to compare some methacrylate based composite at the ultrastructural level and in items of microstructure and topography, and to determine the elemental composition.

Observations on the Sporozoa Inhabiting the Gut of the Polychaete Worm Polydora flava Claparède

Parasitology ◽  
1936 ◽  
Vol 28 (3) ◽  
pp. 414-430 ◽  
Author(s):  
R. Ralph Fowell
Keyword(s):  
Sea Water ◽  
Cyst Formation ◽  
First Record ◽  
The Other ◽  
Intestinal Cells ◽  
Great Abundance ◽  
Polar Groups ◽  
Annelid Worm ◽  
First Time ◽  
A New Species

1. A detailed description is given of a coccidian which parasitises the nuclei of the intestinal cells of the polychaete worm Polydora flava Claparède. The final stages in sporogony have not been observed; nevertheless, this is the first record, from an annelid worm, of an eimeriid which shows a striking resemblance to those Coccidia occurring in the higher animals. It is also the first record of an intranuclear parasite from an annelid.2. From the gut of the same worm, a new species of Selenidium is described. It differs from all other species, hitherto recorded, in the possession of an axial tube, which completely encloses the nucleus and extends from one end of the organism to the other: hence it is proposed to name this organism Selenidium axiferens. The anterior end of the trophozoite shows a circlet of siderophilous bodies, which Ray (1930 a) has shown to be characteristic of the genus.3. Both uninucleate and multinucleate intracellular forms, with polar groups of chromatic globules, have been discovered in great abundance on six occasions; no merozoites have been found, but evidence is submitted to show that these intracellular forms represent the schizogonic phase in the life-cycle of the Selenidium.4. Sporogony follows closely that described for other species, but the final stages have not been observed. The gametocysts measure 48 × 50–70 × 63μ.5. Association and cyst formation are described in Polyrhabdina polydorae Caul. & Mesn. (?) for the first time. Innumerable nuclei make their appearance in each gametocyte, before ejection of the cysts into the sea-water takes place. Gametocysts can easily be distinguished from those of Selenidium axiferens, not only by their morphology, but also by their greater size (98 × 90–105 × 100μ).

scholarly journals Experimental study on using commercial membranes for treatment of wastewater generated by collagen production

2019 ◽  
pp. 50-55
Author(s):  
Mirela Alina Constantin ◽  
Lucian Alexandru Constantin ◽  
Ion Viorel Patroescu ◽  
Gheorghe Batrinescu
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
The Other ◽  
Treated Wastewater ◽  
Biological Processes ◽  
Wastewater Discharge ◽  
Organic Loading ◽  
Membrane Processes ◽  
Collagen Production ◽  
Valuable Compounds

Collagen production is generating wastewater with high organic loading. This type of wastewater is still containing valuable compounds that can be reused in other applications. In order to investigate the possibility to recover and reuse these compounds the membrane based processes were investigated. Four types of commercial available membranes were characterised and then used to recover the proteins. The results proved that membrane based processes represent a viable alternative to treatment of wastewater generated by collagen production facilities when recovery of valuable compounds is envisaged. It has to be stressed that on the other hand only membrane processes do not assure too reach the quality norms imposed by the legislation for treated wastewater discharge into sewerage systems or natural receivers. Therefore, when proteins recovery and reuse is wanted, the membrane processes represent only the first step of wastewater treatment and should be followed by biological processes in order to obtain the organic loading quality indicators required for wastewater treatment plants discharges.

Linear Thermal Expansion of Elastomers in the Range 300° to 76° K

1964 ◽  
Vol 37 (1) ◽  
pp. 154-168 ◽  
Author(s):  
R. F. Robbins ◽  
Y. Ohori ◽  
D. H. Weitzel
Keyword(s):  
Thermal Expansion ◽  
Linear Thermal Expansion ◽  
The Other ◽  
Thermal Contraction ◽  
Cryogenic Temperatures ◽  
Design Data ◽  
Polar Groups ◽  
Other Hand ◽  
Commercial Sources ◽  
Ceramic Fillers

Abstract From the relations between Tg's of the component homopolymers with that of the resulting copolymer, one sees that the limit of the Tg of copolymers is that of the homopolymers. To obtain a low Tg one must avoid polymers with polar groups and/or bulky groups. Polar groups afford opportunities for intermolecular links which hinder rotation necessary for “rubberyness.” Bulky groups cause stiffness, and also serve as obstructions to contractions. On the other hand, the same reasons that polar and bulky groups raise Tg serve to lower overall thermal contraction, since αr is always greater than αg. Fillers can be used to lower contraction, and new ceramic fillers with negative coefficients of expansion might be combined with specific polymers to obtain a material with a desired contraction. The authors feel that the data presented here, together with design data available from commercial sources, should enable the design engineer to find many new uses for elastomers at cryogenic temperatures.

scholarly journals Sorption of Pharmaceuticals in Aqueous Solution Using Insoluble β-Cyclodextrin Polymers

2021 ◽  
Author(s):  
Atefeh S Mirani
Keyword(s):  
Organic Contaminants ◽  
Freundlich Isotherm ◽  
The Other ◽  
Cross Linking ◽  
Condensation Polymerization ◽  
Analytical Technique ◽  
Addition Polymerization ◽  
Cyclodextrin Polymers ◽  
Isotherm Equations ◽  
Pharmaceutical Molecules

The present study was aimed at evaluating the ability of insoluble β-cyclodextrin polymers (βCDps) to recover pharmaceuticals from aqueous solutions. Two different β-cyclodextrin polymers, one composed of epichlorohydrin-cross linked β-cyclodextrin and the other a β-cyclodextrin-polyurethane, were prepared by condensation polymerization and addition polymerization of βCD using epichlorohydrin (EP) and diisocyanatohexane (HDI) as cross linking agents, respectively. The contaminants tested were naphthalene, naproxen, nabumetone, 2-naphthol, pyrene and propranolol which represent model pharmaceutical molecules. The adsorption isotherms of the organics and βCDPs were well described by Freundlich isotherm equations. The trapping efficiencies were determined using fluorescence spectroscopy as the analytical technique. Based on the results of this study, it was found that the epichlorohydrin-cross linked β-cyclodextrin polymers were more efficient in adsorption of organic contaminants both in batch and column systems when compared with β-cyclodextrin-polyurethane polymers. Reasons for these differences are discussed.

scholarly journals Sorption of Pharmaceuticals in Aqueous Solution Using Insoluble β-Cyclodextrin Polymers

2021 ◽  
Author(s):  
Atefeh S Mirani
Keyword(s):  
Organic Contaminants ◽  
Freundlich Isotherm ◽  
The Other ◽  
Cross Linking ◽  
Condensation Polymerization ◽  
Analytical Technique ◽  
Addition Polymerization ◽  
Cyclodextrin Polymers ◽  
Isotherm Equations ◽  
Pharmaceutical Molecules

The present study was aimed at evaluating the ability of insoluble β-cyclodextrin polymers (βCDps) to recover pharmaceuticals from aqueous solutions. Two different β-cyclodextrin polymers, one composed of epichlorohydrin-cross linked β-cyclodextrin and the other a β-cyclodextrin-polyurethane, were prepared by condensation polymerization and addition polymerization of βCD using epichlorohydrin (EP) and diisocyanatohexane (HDI) as cross linking agents, respectively. The contaminants tested were naphthalene, naproxen, nabumetone, 2-naphthol, pyrene and propranolol which represent model pharmaceutical molecules. The adsorption isotherms of the organics and βCDPs were well described by Freundlich isotherm equations. The trapping efficiencies were determined using fluorescence spectroscopy as the analytical technique. Based on the results of this study, it was found that the epichlorohydrin-cross linked β-cyclodextrin polymers were more efficient in adsorption of organic contaminants both in batch and column systems when compared with β-cyclodextrin-polyurethane polymers. Reasons for these differences are discussed.

Network Formation by Association of Polar Groups in Elastomers

1989 ◽  
Vol 62 (2) ◽  
pp. 343-356 ◽  
Author(s):  
N. Nakajima ◽  
C. D. Huang ◽  
J. J. Scobbo ◽  
W. J. Shieh ◽  
E. R. Harrell
Keyword(s):  
Polymer Chain ◽  
Simple Shear ◽  
Network Formation ◽  
The Other ◽  
Chain Entanglement ◽  
Acrylonitrile Copolymer ◽  
Polar Groups ◽  
Other Hand ◽  
Chemical Crosslinks

Abstract If an elastomer containing polar groups forms interchain associations, can we observe them independently from the effect of chain entanglement? Polyethylacrylate and polyepichlorohydrin are polar elastomers. Our previous deformational study indicated that these elastomers contain interchain associations, which are stronger than the physical entanglements. The conclusion was based on the results of large, unidirectional extension and small simple shear measurements. On the other hand, butadiene—acrylonitrile copolymer (NBR) containing 33% acrylonitrile did not indicate a presence of such a strong interchain association. In this work, we examined NBRs containing 40% acrylonitrile. The polar association, though weak, was detected with these elastomers. This indicates that the effective association involves a number of polar groups closely placed along the polymer chain. Also, in this work, nonpolar elastomers, SBRs, were chemically crosslinked and used as models. The polar association turned out to be not as strong as the chemical crosslinks. This indicates that the polar association disengage and reengage during the deformation.

Polymeric biomaterials: influence of phosphorylcholine polar groups on protein adsorption and complement activation

1994 ◽  
Vol 17 (9) ◽  
pp. 499-504 ◽  
Author(s):  
J. Yu ◽  
N.M.K. Lamba ◽  
J.M. Courtney ◽  
T.L. Whateley ◽  
J.D.S. Gaylor ◽  
...  
Keyword(s):  
Protein Adsorption ◽  
Complement Activation ◽  
Marked Reduction ◽  
Blood Compatibility ◽  
The Other ◽  
Butyl Methacrylate ◽  
Polar Groups ◽  
Polymeric Biomaterials

The introduction to polymeric biomaterials of phosphorylcholine polar groups represents an approach towards the development of materials with improved blood compatibility. In this respect, two biomaterials, one a copolymer of butyl methacrylate and 2-methacryloyloxyethylphosphorylcholine (MPC), (poly(BMA-co-MPC) and the other, MPC-grafted Cuprophan, were examined with respect to their influence on protein adsorption and complement activation. Protein adsorption was studied by measurement of the adsorption of radiolabelled single proteins (albumin and fibrinogen), while complement activation was measured using radioimmunoassay for C3a des Arg. The investigation demonstrated that the polymers containing phosphorylcholine polar groups can achieve a marked reduction in protein adsorption and complement activation and supports the utilization of phosphorylcholine polar groups as a means of improving the compatibility of biomaterials for blood-contacting applications.

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